The invention relates to a load limiting device, especially for a seat belt in a vehicle. The invention moreover relates to a method of controlling such load limiting device.
Load limiting devices permit limited extension of the belt webbing when the seat belt blocks so as to reduce the load on the vehicle occupant. Such load limiting device includes braking means which regulates the webbing extension via the element to be decelerated. From the state of the art braking means are known comprising a fluid-filled compartment including a conduit through which the fluid is allowed to flow. In or at the fluid-filled compartment a displacing element is arranged which is coupled to the seat belt via an element to be decelerated and upon blocking of the seat belt or release of the load limiting device is moved inside the fluid-filled compartment so that the fluid flows through the conduit.
By adjusting the fluid quantify flowing through the conduit and, resp., the flow rate in the conduit the resistance counteracting a movement of the displacing element and thus the level of load limitation and, resp., of webbing extension can be adjusted.
In order to achieve highly exact adaptation of the load limiting device e.g. to the weight of the vehicle occupant or the intensity of deceleration, such bad limiting devices include sensors for detecting vehicle operating data, for example of the acceleration of the vehicle, and for detecting the webbing extension as well as a controller. The controller allows controlling the extension of the webbing as a function of the measured data so that the range available for load limitation is perfectly exploited and the load on the vehicle occupant is minimized. In order to ensure most exact control of the braking device it is required to regulate the flow through the conduit as accurately as possible.